Dan...I think it's important to consider what it is you're showing too. While action sequences and editorial style video really should be set such that it takes a limited amount of time to get it rolling for the viewer, and the context isn't dependent on high quality, the lower res versions should work. However, I think it is vital to provide high quality HD to viewers who demand it, especially for context that requires it. Also remember that by showing HD format high quality imagery, you also allow prospective clients know you do shot in HD and that even the lower res video is likely available in higher resolution versions.